When balancing the macro-mineral portion of a petfood, calcium and phosphorus are usually the first priority, magnesium seldom requires adjustment, and sodium and chloride, if inadequate, are easily met with a pinch of salt (sodium chloride). All that remains is potassium.
Potassium is often described in agricultural literature as potash. While in today’s commerce potassium chloride is the primary source of potash, the term dates back hundreds of years and describes a broader array of potassium salts such as potassium carbonate and potassium oxide. The term is literally descriptive of a process for solubilizing ash from burned wood in a pot—thus the term “pot–ash.” The process was used to create lye compounds used in soap manufacture, metal etching and the millenary industries.